Jet propulsion unit for boats

ABSTRACT

This jet unit includes a vertically oriented centrifugal pump having a drive motor mounted above it. The pump housing is disposed between the ends of a longitudinal passage having a forward intake opening at the bottom of the boat and a discharge opening at the stern. A movable venturi unit mounted in the discharge opening provides the boat with a steering capability and circulates motor cooling water. The motor exhaust gas is mixed with water at the pump for discharge with the water through the venturi unit.

United States Patent [1 1 Arnold 1 1 JET PROPULSION UNIT FOR BOATS [76] Inventor: Robert W. Arnold, 819 Merriwether St., Cape Girurdeau, Mo. 63701 [22] Filed: Jan. 31, 1974 [21] Appl. No.: 438,295

[52] US. Cl. 115/16 [51] Int. Cl. B63h'11/04 [58] Field of Search 115/11, 12 R. 16; 60/221, 60/222 [56] References Cited UNITED STATES PATENTS 1,197,181 9/1916 Buck 115/16 2,743,698 5/1956 Leonard et a1. 115/16 3,035,409 5/1962 Pifer 115/16 3,183,878 5/1965 Aschauer 115/16 June 17, 1975 9/1966 Roulund 115/16 3,776,173 12/1973 Horwitz 115/12 R Primary Examiner-Trygve M. Blix Assistant Examiner-Stuart M. Goldstein [57] ABSTRACT This jet unit includes a vertically oriented centrifugal pump having a drive motor mounted above it. The pump housing is disposed between the ends of a longitudinal passage having a forward intake opening at the bottom of the boat and a discharge opening at the stern. A movable venturi unit mounted in the discharge opening provides the boat with a steering capability and circulates motor cooling water. The motor exhaust gas is mixed with water at the pump for discharge with the water through the venturi unit.

2 Claims, 6 Drawing Figures JET PROPULSION UNIT FOR BOATS BACKGROUND OF THE INVENTION This invention relates generally to a jet propulsion unit for a boat and particularly to a unit having an improved steering and circulation system.

Jet units for boats have been used for many years and such units generally consist of a pump driven by a conventional gas engine. Water is drawn in through an inlet forward of the pump stage, accelerated by the pump and discharged at the stern. Various improvement features have been incorporated in the past into this general arrangement. However, in spite of these improvements boats propelled by jet units still form only a small portion of the enormous number of boats in use in the United States and elsewhere. The primary reason for this is believed to result from the relative complexity and inefficient operation of available boats using jet propulsion units.

One known jet propulsion unit, which uses a centrifugal pump having a vertical axis and mounted amidships for the drive unit, is directed to a steering means which utilizes a longitudinal conduit having forked portions forwardly and rearwardly disposed of the drive unit. The forked portions control discharge from ports provided at each side of the hull to effectuate steering. Another jet propulsion unit, also directed primarily to the steering of the boat, provides a deflecting rudder in a fixed, flared tube for controlling forward steering and an independent, reversely angled dual tube for controlling rearward steering. This propulsion unit utilizes a horizontal axis screw type pump.

Neither of these units nor any other known units incorporate the advantageous features employed in the present invention.

SUMMARY OF THE INVENTION This jet unit is intended primarily for small craft and provides a centrifugal pump impeller having a vertical axis of rotation and mounted below a drive motor. The pump impeller is located intermediate a longitudinal conduit, which extends between a forwardly disposed intake opening and a rearwardly disposed discharge opening, said discharge opening having a venturi unit mounted therein in swivel relation for steering. The motor is water cooled by a siphon supply system actuated by the venturi located at the discharge opening. The exhaust gas from the drive motor is directed into the impeller housing and discharged through the venturi by the action of the impeller.

This jet unit is relatively simple and inexpensive to manufacture and can be operated efficiently without special instructions.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view of a boat provided with the jet propulsion unit;

FIG. 2 is a plan view thereof;

FIG. 3 is an enlarged, fragmentary view of the stern taken on line 33 of FIG. 1;

FIG. 4 is an enlarged, fragmentary cross section of the stern through the longitudinal centerline of the boat;

FIG. 5 is an enlarged elevational view of the cage impeller; and

FIG. 6 is an enlarged plan view of the underside of the cage impeller.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now by characters of reference to the drawing and first to FIGS. 1 and 2 it will be understood that the jet propulsion unit, which is generally indicated by numeral 10, is mounted within the hull 12 of a relatively small power boat 11. Apart from the jet propulsion unit the boat 11 may be of substantially conventional design and, as shownjincludes a prow 13 and a stem 14 constituting forward and rearward ends of the hull respectively. The jet unit 10 is mounted in the stern of the boat in a compartment 15 provided with a hatch cover 16. The jet unit 10 consists essentially of a drive motor 17 disposed above and connected in drive relation to a centrifugal pump 20, which draws water from a forwardly disposed first passage 21 for discharge through a rearwardly disposed second passage 22 having a venturi unit 23 mounted therein.

Turning now to a more specific description of the individual parts and referring to FIGS. 3 through 6, it will be seen that the drive motor-17, which is shown in phantom outline in FIGS. 3 and 4, is provided with a water jacket 24 through which water circulates as will be described. The centrifugal pump 20 includes a cagetype impeller 25 having a drive shaft 26 attached thereto in fixed relation by means of a boss 27. The drive shaft 26 defines a vertical axis of rotation and is connected to the motor 17 in drive relation, and a journal seal 28 is provided to facilitate the drive connection. The impeller 25 rotates within a substantially annular housing 31, which is defined by upper and lower side plates 32, and inner and outer circumferential plates 34 and 35. The housing 31 also includes an upper cylindrical portion 36 having a flange 37 which is connected to the motor and water jacket assembly.

As shown clearly in FIGS. 5 and 6 the cage impeller 25 includes upper and lower spaced plates 40 and 41, respectively, separated by a plurality of curved vanes 42, which are attached to said plates as by welding. The bottom plate 41 includes an axial inlet opening 43 defined by a cylindrical rim 44. As clearly shown in FIG. 4 the upper and lower plates 40 and 41 of the impeller 25 are disposed in parallel spaced relation from associated upper and lower plates 32 and 33 of the housing 31. The impeller axial opening 43 is disposed in register with a substantially vertical cylindrical portion of the forward passage 21. This vertical portion 45 provides a transition between a convergent portion 46 of said passage 21, which extends rearwardly from an intake opening 47, and said axial opening 43. Water discharged centrifugally from the impeller 25 enters the rearward passage 22, which is integrally formed with the inner circumferential wall 34 of the housing 31 at the housing end of said passage and is formed into a socket portion 50 at the discharge end. The socket portion 50 receives a compatibly configurated ball portion 51 of the venturi unit 23, to provide said unit 23 with a ball joint connection which permits said unit to be swiveled substantially universally, and in particular from side to side, substantially in the horizontal plane, so that the nozzle portion 52 can be directed laterally from port to starboard by suitable mechanism (not shown) to steer the boat.

As noted above, the drive motor 17 is water cooled and to this end is provided with the water jacket 24. Water is circulated through the water jacket 24 by utilizing the venturi unit 23 in combination with first and second conduits 53 and 54 respectively. Conduit 53 is connected to the lower portion of the jacket 24 and depends downwardly so that the open end 55 is received within the converging portion 46 of the forward passage 21. The conduit 54, which in the preferred embodiment is a flexible hose, is connected to the upper portion of the water jacket 24 and depends downwardly to be received within the rearward passage 22 and extends also longitudinally so that the open end 56 is disposed coaxially in the vicinity of the venturi throat indicated by numeral 57. It will be understood that the venturi action at the throat 57 draws water through the conduit 54 from the water jacket 24 and that water is thereby picked up from the passage 21 by the conduit 53 by a siphoning type of action to provide a continuous circulation of cooling water while the drive motor is in operation.

As clearly shown in FIG. 4 the motor exhaust port, indicated by numeral 60, is discharged into the impeller housing portion 36 by means of an exhaust conduit 61. Because of the structural relationship between the impeller 25 and the housing 31, a negative pressure exists between the impeller upper plate 40 and the housing upper plate 32 when the centrifugal pump is operational. This negative pressure draws exhaust gas through the housing 31 and hence into the rearward passage 22 for discharge through the venturi unit 23. This arrangement, by which exhaust gases are mixed with the water passing through the pump, tends to break up sound waves and makes a very effective muffler for the motor exhaust system.

It is thought that the structural features and functional advantages of this jet propulsion unit have become fully apparent from the foregoing description of parts but for completeness of disclosure the operation will be briefly summarized.

As shown in FIG. 1 the intake opening 47 and the venturi unit 23 are both disposed below the surface of the water under normal operating conditions. When the centrifugal pump 20 is actuated by the motor 17 water is drawn, by way of the intake opening 47, through the forward passage 21 for centrifugal discharge by the pump 20 through the rearward passage 22 and the venturi unit 23. By suitable alignment of the venturi nozzle 23 the boat can be propelled and steered in the direction desired. The venturi unit 23, in addition to performing the function of steering the boat, provides a means of cooling the motor in that the provision of conduits 53 and 54 extending from the water jacket 24 to the forward intake passage 21 and the venturi throat 57, respectively, provides a means by which the water in the jacket is continuously circulated through the jacket.

As clearly shown in FIGS. 3 and 4 the passage extending rearwardly of the intake opening 47 converges in such a manner as to provide a decreasing cross section of area as it approaches the pump axial opening 43. This structural arrangement not only facilitates the supply of water to the pump impeller 25 but also provides, in effect, a reserve supply of water large enough to supply the hydraulic medium to the pump in those instances when the boat hull, in the vicinity of the intake opening 47, momentarily emerges from the water.

The jet unit 10 is particularly quiet and vibration free because of the efficiency of the exhaust system. This efficiency is primarily the result of utilizing the partial vacuum which exists between the housing 31 and the impeller 25, to draw the exhaust from the drive motor 17 into the stream of discharged water. This feature is particularly useful on a two-cycle motor, which is designed to operate with an underwater exhaust.

I claim as my invention:

1. In combination with a boat, a jet propulsion unit comprising:

a. a boat hull including forward and rearward ends and having an intake opening intermediate said ends and a discharge opening at the rearward end disposed below the water line,

b. a drive motor,

c. a centrifugal pump mounted between said intake and discharge openings and including:

1. an impeller having a drive shaft, said shaft defining a substantially vertical axis of rotation and being connected to the motor in drive relation, and a coaxial inlet opening, and

2. a housing receiving the impeller in rotatable relation,

d. a first intake passage extending longitudinally between the intake opening and the inlet opening of the pump impeller,

e. a second discharge passage extending longitudinally between the pump housing and the discharge opening,

f. a venturi unit mounted in the discharge passage,

and

g. cooling means for the motor including:

1. a water jacket disposed about said motor,

2. a first conduit extending between the first passage and the water jacket, and

3. a second conduit extending between the water jacket and the venturi throat to draw cooling water from the jacket by suction and thereby pick up water from the first passage through the first conduit for circulation through said jacket.

2. A jet propulsion unit as defined in claim 1, in

which:

h. the motor includes an exhaust port,

i. the impeller includes spaced upper and lower plates separated by a plurality of vanes,

j. the impeller housing is spaced from said impeller to define a negative pressure area between said housing and impeller communicating with said second passage, and

k. exhaust conduit means communicates between the exhaust port and said negative pressure area whereby exhaust gas is drawn into the impeller housing and into said second passage when said impelier rotates. 

1. In combination with a boat, a jet propulsion unit comprising: a. a boat hull including forward and rearward ends and having an intake opening intermediate said ends and a discharge opening at the rearward end disposed below the water line, b. a drive motor, c. a centrifugal pump mounted between said intake and discharge openings and including:
 1. an impeller having a drive shaft, said shaft defining a substantially vertical axis of rotation and being connected to the motor in drive relation, and a coaxial inlet opening, and
 2. a housing receiving the impeller in rotatable relation, d. a first intake passage extending longitudinaLly between the intake opening and the inlet opening of the pump impeller, e. a second discharge passage extending longitudinally between the pump housing and the discharge opening, f. a venturi unit mounted in the discharge passage, and g. cooling means for the motor including:
 1. a water jacket disposed about said motor,
 2. a first conduit extending between the first passage and the water jacket, and
 3. a second conduit extending between the water jacket and the venturi throat to draw cooling water from the jacket by suction and thereby pick up water from the first passage through the first conduit for circulation through said jacket.
 2. A jet propulsion unit as defined in claim 1, in which: h. the motor includes an exhaust port, i. the impeller includes spaced upper and lower plates separated by a plurality of vanes, j. the impeller housing is spaced from said impeller to define a negative pressure area between said housing and impeller communicating with said second passage, and k. exhaust conduit means communicates between the exhaust port and said negative pressure area whereby exhaust gas is drawn into the impeller housing and into said second passage when said impeller rotates.
 2. a first conduit extending between the first passage and the water jacket, and
 2. a housing receiving the impeller in rotatable relation, d. a first intake passage extending longitudinaLly between the intake opening and the inlet opening of the pump impeller, e. a second discharge passage extending longitudinally between the pump housing and the discharge opening, f. a venturi unit mounted in the discharge passage, and g. cooling means for the motor including:
 3. a second conduit extending between the water jacket and the venturi throat to draw cooling water from the jacket by suction and thereby pick up water from the first passage through the first conduit for circulation through said jacket. 